An electronic component is manufactured using a substrate made of an inorganic material in order to guarantee the dynamic durability and electrical insulation property. Typical examples of inorganic material substrates that are used include substrates of oxides such as silicate glass, alumina, and quartz, substrates of nitrides such as silicon nitride, and aluminium nitride, substrates of carbides such as silicon carbide and titanium carbide, and silicon substrates. Conductive electrodes (wiring) should be formed on a substrate in order to produce an electronic component using such a substrate or mounting a semiconductor, a capacitor, a resistor, and the like on the substrate.
Conductive materials such as silver and copper are used for such conductive electrodes. Silver is excellent in conductivity and oxidation resistance, however, it is expensive and also has disadvantages such that silver atom migration failure easily takes place. In contrast, copper has a material cost lower than that of silver, is excellent in migration resistance, and has electric resistivity equivalent to that of silver, so that the use of copper for a conductive electrode is desired.
Conventionally, methods known for forming copper electrodes on inorganic material substrates such as glass substrates are an electroless plating method and a method that involves applying a copper paste produced by mixing with a copper powder and baking. However, these methods are problematic in that the adhesion of copper to an inorganic material substrate is insufficient so that copper electrodes formed on an inorganic material substrate are easily peeled off.
To overcome such a problem concerning adhesion, for example, the formation of an electroless copper plated film, followed by application of plus potential and heating of the substrate simultaneously (Patent document 1), and the use of a copper paste composition prepared by mixing a copper powder, a copper oxide powder, a Pd compound, and a glass frit (Patent document 2) have been proposed.
Moreover, the formation of an interface layer between an inorganic material substrate and a copper electrode has also been proposed. For example, patent document 3 proposes to form a base film comprising a copper alloy film that contains oxygen, Mn, and Ag, patent document 4 proposes to form a zone where components of Cu, Ca, oxygen and Si are aggregated between a silicon oxide film and a copper film, and patent document 5 proposes the presence of a metal oxide containing at least one type of a cuprous oxide, a nickel oxide and a cobalt oxide in the contact interface between an insulating resin substrate and a metal thin film layer.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2007-31741    Patent Document 2: Japanese Unexamined Patent Application, Publication No. H08-45339    Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2009-10089    Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2010-103324    Patent Document 5: Japanese Unexamined Patent Application, Publication No. 2011-104815